Operational Energy: Why it matters and who owns the responsibility?

Today, there’s a growing expectation for designers to predict, and even influence, a building’s total operational energy use, which includes both regulated and unregulated components. The latter encompasses everything from IT and lab equipment to catering and specialist machinery, elements that are often outside the designer’s direct control. 

Facing the Challenge of Unregulated Energy 

It’s tempting for designers to distance themselves from unregulated energy use. After all, how can we be held accountable for how occupants behave or what equipment they use? While this argument holds some truth, it overlooks what truly matters to building owners: real-world energy performance and operational costs. 

That’s why it’s essential to engage clients early in the design process. These conversations should cover the limitations of energy prediction tools, the impact of occupant behaviour, and the importance of designing with flexibility and efficiency in mind. 

Why Total Operational Energy Matters 

Clients are increasingly driven by more than just cost, they’re also under pressure to meet internal and external carbon targets. In some cases, this includes strict caps on emissions from new developments. By addressing total energy use, we can: 

• Provide more accurate forecasts of energy consumption and emissions 
• Enable targeted interventions for behaviour change and system optimisation 
• Deliver buildings that support efficient, sustainable operation 

Who Owns the Responsibility? 

Regulated energy is embedded in the building’s design and systems. While usage patterns may vary, designers can ensure these systems are as efficient as possible. 

Unregulated energy, however, is more fluid. It often isn’t fully defined until late in the design process and can fluctuate throughout the building’s life. In some cases, it can account for up to 50% of total energy use. 

While designers can’t control every variable, we can work collaboratively with clients to predict and mitigate unregulated energy use through thoughtful design and informed decision-making. 

Designing for Influence 

Facilities managers and occupants ultimately control unregulated energy use, but design can either support or hinder efficient behaviour. Strategies we’ve implemented include: 

• Centralised shared facilities to reduce redundant equipment 
• Master shut-off switches and accessible sockets to encourage power-down habits 
• Dedicated storage to prevent misuse of energy-intensive systems like fume cupboards 
• Energy dashboards to raise awareness and promote behavioural change 
• Infrastructure for green IT and post-occupancy evaluations to fine-tune performance 

Tools for Prediction: TM54 

The most robust method currently available is CIBSE’s Technical Memorandum 54 (TM54), which provides guidance for estimating operational energy based on intended use. Case studies show TM54 can predict energy use within 15% accuracy. 

Despite its value, uptake has been limited, often due to cost. For large buildings, TM54 assessments can cost up to £30,000. That’s why it’s important to discuss the cost-benefit of TM54 early in the project lifecycle. 

The Rebound Effect: A Hidden Complication 

Even with efficient systems in place, behavioural responses can offset gains, a phenomenon known as the rebound effect. For example, users may leave energy-saving lights on longer, assuming they’re less costly to run. 

While difficult to quantify, this effect underscores the importance of client education and occupant engagement in achieving meaningful energy reductions. 

A Shared Responsibility 

Clients are becoming more aware of the importance of total operational energy. For designers, this means embracing the challenge of unregulated energy, not as a burden, but as an opportunity to add value. 

By initiating early conversations, designing with intent, and supporting informed decision-making, we can help clients create buildings that perform efficiently in the real world, not just on paper.